Treatment of hydrocarbon oil



TREATMENT 01 HYDROCARBON OIL Filed-May s1, 1 1955 INVENTOR JOHN T W120BMW ATTORNEY Patented Sept. 515, i938 PATENT OFFICE murmur orHYDROOABBON on. John T. Ward, Weltileld, N. 1., alsllnor to lineProducts Company, Inc., corporation of Delaware .Galo- Newark, N. 1., a

\ Application May 31, 1933, Serial N0 618,618

4Claims.

This invention relates to the art of pyrolytically treating hydrocarbonoils, more particularly crude petroleum oils containing waxyconstituents of both pressable and non-pressable. nature, for therecovery of valuable products therefrom. Certain crude oils, forexample, of the Pennsylvania and Mid-Continent types contain wax in aform readily recovable by pressing from the distillatefractionin whichit is initially recovered and generally known as crystalline wax, aswell as wax which is dimcult or impossible to recover by pressing fromthe somewhat heavier fraction in which it is found. Wax in this latterform is sometimes known as amorphous wax by reason of the difficultyencountered in removing it, although actually itmay be similar to oridentical with wax known as crystalline wax except as to crystallinesize or structure.

My invention has for an object the provision of a process for theremoval of a maximum amount of wax in pressable or crystalline form froma crude petroleum oil containing waxy constitutents and adapted to bringwax which would ordinarily be obtained in non-pressable form intopressable wax. 7

My invention has for further objects such further operative advantagesand improvements as may hereinafter be found to obtain.

' wax fraction.

The heavy fraction containing amorphous or non-pressable wax issubjected to moderate cracking conditions in a separate coil providedfor that purpose and is delivered to a. separate fractionating stage,the wax fraction previously recovered from the initial fractionationstage preferably being commingled with the stream of cracked products.The separate or secondary fractionation stage is operated in such amanner as to effect the condensation of all constituents up to andincluding such amorphous or nonpressable wax as may remain after thecracking operation. The condensates are separated into various cuts,including a fraction containing the (CL 19H!) pressable wax, one or morefractions of lighter materials, and a heavier or "slop wax cut, whilethe residual products are withdrawn as fuel oil.

The slop wax cut containing amorphous or nonpressable wax is preferablyrecycled in the cracking operation to increase the yield of pressablewax.

My invention thus makes it possible to obtain a maximum yield ofpressable wax by avoiding unnecessary cracking of wax initiallyrecoverable in pressable form, while subjecting the initial yield ofamorphous or non-pressable wax to an operation which tends to producewax in pressable form and at the same time reduces to a minimum loss oflubricating oil constituents through pyrolysis.

The action which takes place in the cracking coil may be either anactual conversion of amorphous wax (protoparaflln) to crystalline wax(paroparaflin) or it may be a decomposition and removal of certainviscousoils or other hydrocarbon materials, the presence of which tendsto hinder crystallization or separation of the true wax, and I do notlimit myself to any particular theory as to the precise nature of theaction which takes place, but in any, event theeflect of the cracking inthe secondary stage is to increase the yield of pressable wax and todiminish or eliminate the quantity of theyield of wax present in anon-pressable form, irrespective of whether the chemical or physicalnature of the wax itself has been altered in the process.

In order that my invention may be clearly set forth and understood, Inow describe, with reference to the drawing accompanying and forming apart of this specification, a preferred manner in which my invention maybe practiced and carried out. In this drawing, the single figure is amore: or less diagrammatic representation of a flow sheet of a preferredform of my process.

Referring to the figure, a crude-petroleum 011 containing a considerableamount of waxy constituents enters the system through a conduit I inwhich is located a pump 2 and heat exchangers 3, l, 5 and 6. The oilpassesthrough the heat exchangers 3, A, I. and 6 and is then supplied inpreheated form" to a convectioncoil I within .a furnace 8. The oil afterleaving the convection coil I passes through a radiation coil 9 where itis brought to a suitable distillation temperature, for example, about700 F. and preferably not over. 750' F. The oil at this temperature thenpasses through a further convection coil ill and leaves thefurnace 8through a conduit I2 leading to the lower portion of a fractionatingtower I3,

The fractionating tower I3 may be of conventional design and providedwith suitable plates or trays I4 and also with an inlet I5 forsuperheated steam.

By means of reflux delivered to the tower I3 through conduits I8 and II, the vapors liberated in the lower portion of the tower I3 arefractionally condensed into a plurality of fractions which are removedfrom the tower I3 through a corresponding plurality of outlets 20 to 25,while the residual products are withdrawn from the bottom of the towerI3 through an outlet 28. Vapors which are not condensed in the tower I3pass through an overhead vapor line 21, through the heat exchanger 3where they are partially cooled by indirect contact with the incomingcrude oil, to a condenser 28 where they are further cooled to such anextent as to condense out substantially all constituents of a normallyliquid character. The condensed products pass through a conduit 29through a gas separator 30 from which separated gas is withdrawn througha conduit 3i. A portion of the gasoline or other condensate is withdrawnfrom the separator 38 through an outlet pipe 3I' having a pump 32 whichdelivers it through the conduit I6 to the upper portion of the tower I3as reflux, while the remaining portion of the condensate is removed fromthe separator 38 through an outlet 33.

The various fractions ranging from naphtha to and including gas oil,which are withdrawn from the tower I3 through outlets 28 to 24, arepassed to strippers 48 to 44 respectively while the fraction recoveredand removed from the tower I3 through the outlet 25 is delivered to astripper 45. The stripped products from the stripping sections 48 to 44are withdrawn through outlets 46 to 58 and delivered to coolers 5i to86, respectively, from which they are withdrawn for storage or forfurther treatment.

A portion of the oil withdrawn through one of the outlets 28 to 24, forexample, refined oil, which is withdrawn from the tower I3 through theconduit 23, is taken off through a conduit 51 and after passing throughthe heat exchanger 4 where it gives up a portion of its heat to theincoming crude oil, is returned through a conduit 58, a pump 59 and theconduit IT to an intermediate level in the tower I3 as reflux.

The amount and conditions of refluxing are so regulated as to makepossible the recovery through the outlet 25 of a fraction containing thegreater portion of the pressable or crystalline wax but substantiallyfree from amorphous or non-pressable wax, while the residual oil.removed from the bottom of the tower I3 through the conduit 26 containssubstantially all of the amorphous wax as well as a small amount ofpressable wax not recovered in the stream leaving the tower I3 throughthe conduit 25, as well as lubricating oil stock and asphaltic bottoms.

In order to effect the conversion of the amorphous or non-pressable waxin the residual oil leaving the tower I3 through the outlet 26 topressable or crystalline wax, this hot residual oil is delivered bymeans of a pump 6i and the conduit 62 to a radiation coil 63 within thefurnace 8 where it is brought to conditions of pressure and temperaturewhich are effective to promote a moderate cracking of constitutents ofthe oil, for example, a temperature of from 800 to 875 F. and a pressureof around 200 pounds per square inch. The oil then passes through aconvection coil 84 where it is maintained for a short additional periodof time under these cracking conditions of temperature and pressure andthen passes through a conduit to an auxiliary fractionating tower 86. Tothe stream of partially cracked products leaving the coils 83 and 84, Ipreferably add the wax distillate withdrawn from the tower I3 throughthe outlet 25, which distillate after passing through the stripper 45 isdelivered by a pump 61 through a conduit 88, through the heat exchanger5 and a preheater 89 to the conduit 88 which serves to carry the streamof cracked products from the coil 64 to the auxiliary fractionatingtower 86.

In the lower part of the fractionating tower 88 a separation of thecracked products into volatilized and non-volatilized or residualproducts takes place, the residual products collecting in the bottom ofthe tower 66 being withdrawnthrough a conduit II' to be forced by a pumpI2 through the heat exchanger 8 and a cooler I3. These residual productsare useful as fuel oil.

During the passage of the vapors upward through the tower 68 afractional condensation is efiected by means of reflux introduced to theupper portion of the tower 68 through the conduit I4. A side streamconsisting of heavy wax distillate, which contains substantially all ofthe pressable wax and is substantially free from nonpressable oramorphous wax, is withdrawn from the tower 66 through an outlet I5 andpasses to a stripper I8, the stripped heavy wax distillate being thendelivered through a conduit II by means of a pump I8 to a cooler I8.After leaving the cooler I9, the heavy wax distillate is withdrawn andprocessed in the usual manner for the recovery of wax therefrom.

A lighter fraction which may comprise a gas oil is withdrawn from ahigher point in the tower 66 through an outlet 8| leading to a cooler82, while uncondensed vapors pass through an overheadline 83 and througha condenser 84 to a gas separator 85. Gas removed in the separator 85 iswithdrawn through a conduit 88. A portion of the cracked distillatewhich is recovered in the separator 85 is returned by means of a conduit81 and pump 88 and the conduit I4 to the top of the tower 68 for use asreflux, while the remaining portion of the cracked distillate iswithdrawn from the separator 85 through an outlet 83.

For the purpose of removing a slop wax fraction containing suchamorphous or non-pressable wax as is volatilized in the lower portion ofthe tower 86, I provide a suitable trapout tray 8|, the slop waxfraction being withdrawn through the trap-out tray 9i through a conduit82 having a pump 93 and delivered through a conduit 84 to mingle withthe stream of residual oil from the tower I3 which is about to enter thecracking coils 63 and 64. This recycling of the slop wax fraction isadvantageous in that it further assists in bringing the amorphous ornon-pressable wax into a crystalline or pressable condition and inreducing or eliminating the amount of nonpressable wax removed from thesystem, at the same time increasing the yield of pressable wax.

A vapor return conduit 95 is provided for the purpose of returningvapors from the strippers 48 to 45 to the tower I3 and a similar vaporreturn conduit 96 is provided for the purpose of returning vaporsliberated in the stripper 18 to the tower 68.

In the operation of my process the pressures maintained in the towers I3and 88 are as low as it is possible to maintain them and stillaccomplish the passage of the vapors therethrough. Thus the pressure onthe tower l3 may be up to 50 pounds per square inch at the outlet andpossibly as high as 200 pounds per square inch at the inlet, while thepressures in the tower 66 may be of the order of 50 pounds per squareinch or less.

The wax distillate removed from the tower l3, which as aforesaidrepresents a fairly large cut of wax distillate, should ordinarily havea boiling point range of 600 to 750 F. and the outlet temperatures atthe bottom of thetower i3 are ordinarily maintained at from 650 to 700F. On the other hand, the wax distillate removed from the tower 66through the conduits I5 and I1, due to the increase in the amount ofpressable wax and the decrease in the amount of non-pressable wax mayhave a considerable narrower boiling point range of, for example, from625 to 700 F.

It will be obvious to those skilled in the art, however, that suchtemperatures and pressures as have been given hereinabove by way ofspeciflc example may be considerably varied in accordance with thenature of the crude material treated and the results desired.

My invention is, therefore, not limited to the specific details givenhereinabove by way of illustrative example but may variously be embodiedwithin the scope of the claims hereinafter made.

7 I claim:

1. The process of. recovering pressable wax from a crude petroleum oilcontaining wax constituents in pressable and non-pressable form, whichcomprises distilling said oil, separating the products of distillationinto a fraction containing pressable wax substantially free fromnon-pressable wax, lighter products and heavy material containing thebulk of the non-pressable wax, subjecting said heavy material to acracking operation to bring non-pressable wax constituents intopressable form, combining the resultant cracked products with saidpressable wax fraction, and separately subjecting the volatilizedportion of the mixture to fractional condensationto recover therefrom apressable wax distillate. i

2. The process of. recovering pressable wax from a crude petroleum oilcontaining wax constituents in pressable and non-pressable form, whichcomprises distilling said voil, separating the products of distillationinto a fraction containing pressable wax substantially free fromnon-pressable wax, lighter products and heavy material containing thebulk of the non-pressable wax, subjecting said heavy material to acracking operation to bring non-pressable wax constituents intopressable form, combining the resultant cracked products with saidpressable wax fraction, separately subjecting the volatilized portion ofthe mixture to fractional condensation to recover therefrom a pressablewax distillate, and a slop wax cut containing non-pressable wax, andcommingling said slop wax fraction with said heavy material for furthercracking.

3. The process of recovering pressable wax from a crude petroleum oilcontaining wax constituents in pressable and non-pressable form, whichcomprises distilling said oil at a temperature of not more than 750 F.,separating the products of distillation into a fraction containingpressable wax substantially free from non-pressable wax, lighterproducts and heavy material containing the bulk of the non-pressablewax, subjecting said heavy material to a cracking operation at atemperature of from 800 to 850 F. to bring nonpressable wax constituentsinto pressable form, combining the resultant cracked products with saidpressable wax fraction, separately subjecting the volatilized portion ofthe mixture to fractional condensation to recover therefrom a press.-

able wax distillate and a slop wax out containing non-pressable wax, andcommingling said slop wax fraction with said heavy material for furthercracking.

4.- The process of recovering pressable wax from a crude petroleum oilcontaining wax constituents in pressable and non-pressable form, whichcomprises distilling said oil at a temperature of not more than 750 F.,separating the products of distillation into a fraction containingpressable wax substantially free from non-pressable wax and having aboiling point range of from 600 to 750 F., lighter products and heavymaterial containing the bulk of the non-pressable wax, subjecting saidheavy material to a cracking operation at a temperature of from 800 to850 F. to bring non-pressable wax constituents into pressable form,combining the resultant cracked products with said pressable waxfraction, separately subjecting the volatilized portion of. the mixtureto fractional condensation to recover therefrom a pressable waxdistillate and a slop wax cut containing non-pressable wax, andcommingling said slop wax fraction with said heavy material for furthercracking.

JOHN T. WARD.

